Satellite sun‐induced chlorophyll fluorescence detects early response of winter wheat to heat stress in the Indian Indo‐Gangetic Plains

Abstract

Extremely high temperatures represent one of the most severe abiotic stresses limiting crop productivity. However, understanding crop responses to heat stress is still limited considering the increases in both the frequency and severity of heat wave events under climate change. This limited understanding is partly due to the lack of studies or tools for the timely and accurate monitoring of crop responses to extreme heat over broad spatial scales. In this work, we use novel spaceborne data of sun-induced chlorophyll fluorescence (SIF), which is a new proxy for photosynthetic activity, along with traditional vegetation indices (Normalized Difference Vegetation Index NDVI and Enhanced Vegetation Index EVI) to investigate the impacts of heat stress on winter wheat in northwestern India, one of the world's major wheat production areas. In 2010, an abrupt rise in temperature that began in March adversely affected the productivity of wheat and caused yield losses of 6% compared to previous year. The yield predicted by satellite observations of SIF decreased by approximately 13.9%, compared to the 1.2% and 0.4% changes in NDVI and EVI, respectively. During early stage of this heat wave event in early March 2010, the SIF observations showed a significant reduction and earlier response, while NDVI and EVI showed no changes and could not capture the heat stress until late March. The spatial patterns of SIF anomalies closely tracked the temporal evolution of the heat stress over the study area. Furthermore, our results show that SIF can provide large-scale, physiology-related wheat stress response as indicated by the larger reduction in fluorescence yield (SIF ) than fraction of photosynthetically active radiation during the grain-filling phase, which may have eventually led to the reduction in wheat yield in 2010. This study implies that satellite observations of SIF have great potential to detect heat stress conditions in wheat in a timely manner and assess their impacts on wheat yields at large scales.

Widespread Decline in Vegetation Photosynthesis in Southeast Asia Due to the Prolonged Drought During the 2015/2016 El Niño

“…The effects of vegetation structural variables were eliminated, then important information on drought events could be provided by SIF yield . Changes on vegetation greenness and chlorophyll content may not rapidly reflect the information about vegetation status under drought, but variations on the production of fluorescence have rapid responses to water stress [26,29,30,58]. Therefore, SIF yield is the suitable factor to detect the changes of vegetation function during the drought period in the study areas.…”

Estimating and understanding crop yields with explainable deep learning in the Indian Wheat Belt

“…Decreased penetration of sunlight for the crop has already spurred demand for breeding for high photosynthetic or radiation-use efficiency (Joshi et al 2007). These observations also suggest that sun-induced fluorescence could be a good direct proxy for the crop yield, as it carries information on light conditions, and was previously shown to perform better than VIs for yield estimation (Song et al 2018). Although NIRv was found superior to other VIs for estimating GPP (Badgley et al 2017), we did not detect any benefit of using it for the yield estimation.…”

“…Comparison of performances among models with one or two input variables, as well as the RAM analysis, showed that high yields in 2012 were associated with low temperatures accompanied by sunny conditions during the growing period, though most recent studies focus primarily on the impact of increasing temperatures in the Indian Wheat Belt (e.g. Duncan et al 2014, Jain et al 2017, Song et al 2018 and in other regions (Lobell et al 2005). As an important driver of photosynthesis, SW down affects the resources that crops can build during the growing season, which is apparently not fully reflected in the VIs.…”

Effects of oak powdery mildew (Erysiphe alphitoides [Griffon and Maubl.] U. Braun and S. Takam.) on photosynthesis of pedunculate oak (Quercus robur L.)

“…Although it has been proven and well documented that oak powdery mildew has negative effects on the photosynthesis and transpiration of leaves (Hajji et al, 2009;Pap et al, 2014;Copolovici et al, 2014), there is a further need for better understanding the effects of this obligate leaf parasite on the photosynthetic apparatus, due to its complexity. For that purpose, chlorophyll a fluorescence measurement can provide useful additional information for understanding the primary events of photosynthesis and the effects of stress on photochemistry (Razavi et al, 2008;Ajigboye et al, 2016;Guo et al, 2016;Song et al, 2018). The main objective of this study was to access the impact of E. alphitoides on the leaf physiology, using non-destructive fluorescence parameters in combination with parameters of leaf gas exchange.…”